Bipolar plate and electrochemical cell comprising such a bipolar plate

Abstract

A bipolar plate for an electrochemical cell contains two plate elements between which a flow field has a flow inlet and a flow outlet. The flow field has coolant flowing through it. Each plate element has a contact plane for making contact with the respective other plate element and a plurality of first embossments project from the contact plane and face away from the other plate element. One of the plate elements has second embossments. Both the first and the second embossments have an aperture to the contact plane of the plate element. Flow channels are formed by the apertures by having the embossments of the two plate elements offset against one another such that each embossment only partially overlaps one embossment of the other plate element. The second embossments are smaller than the first embossments such that the flow channels are restricted in the second embossments.

The invention claimed is: 
     
       1. A bipolar plate for an electrochemical cell, the bipolar plate comprising:
 two plate elements; 
 a flow field disposed between said two plate elements and having a flow inlet and a flow outlet for a coolant flowing through said flow field; 
 each of said plate elements having a contact plane for contacting a respective other one of said plate elements and a plurality of first protrusions projecting from said contact plane and facing away from said respective other plate element between said flow inlet and said flow outlet; 
 at least one of said plate elements between said flow inlet and said flow outlet having second protrusions, said first and second protrusions having an aperture formed therein toward said contact plane of said plate elements, wherein flow channels being formed by means of said apertures of said first and second protrusions in that said first and second protrusions of said two plate elements being offset relative to one another such that each of said first and second protrusions only partially overlaps at least one of said first and second protrusions of said respective other plate element; 
 said second protrusions being smaller than said first protrusions, so that said flow channels are constricted or interrupted in a region of said second protrusions; and 
 said second protrusions disposed in a region of a connecting line between said flow inlet and said flow outlet. 
 
     
     
       2. The bipolar plate according to  claim 1 , wherein remote from the connecting line between said flow inlet and said flow outlet, only said first protrusions are provided. 
     
     
       3. The bipolar plate according to  claim 1 , wherein at least one group of at least two said second protrusions is provided. 
     
     
       4. The bipolar plate according to  claim 3 , wherein said at least one group contains at least two said second protrusions disposed immediately adjacent to one another. 
     
     
       5. The bipolar plate according to  claim 3 , wherein said at least one group is formed by an alternating sequence of said first protrusions and said second protrusions. 
     
     
       6. The bipolar plate according to  claim 3 , wherein said at least one group is one of at least two groups of said second protrusions, one of said at least two groups is closer to said flow inlet and another of said at least two groups is closer to said flow outlet. 
     
     
       7. The bipolar plate according to  claim 1 , wherein said second protrusions are symmetrically distributed. 
     
     
       8. The bipolar plate according to  claim 1 , wherein only one of said two plate elements has said second protrusions. 
     
     
       9. The bipolar plate according to  claim 1 , wherein said first and second protrusions are stamped impressions in a material of said plate elements. 
     
     
       10. The bipolar plate according to  claim 1 , wherein said first protrusions are configured as knobs with a circular cross-section. 
     
     
       11. The bipolar plate according to  claim 1 , wherein said second protrusions are knobs with a semicircular cross-section. 
     
     
       12. An electrochemical cell, comprising:
 at least one bipolar plate, containing:
 two plate elements; 
 a flow field disposed between said two plate elements and having a flow inlet and a flow outlet for a coolant flowing through said flow field; 
 each of said plate elements having a contact plane for contacting a respective other of said plate elements and a plurality of first protrusions projecting from said contact plane and facing away from said respective other plate element between said flow inlet and said flow outlet; 
 at least one of said plate elements between said flow inlet and said flow outlet having second protrusions, said first and second protrusions having an aperture formed therein facing toward said contact plane of said plate element, wherein flow channels being formed by means of said apertures of said first and second protrusions in that said first and second protrusions of said two plate elements being offset relative to one another such that each of said first and second protrusions only partially overlaps at least one of said first and second protrusions of said respective other plate element; 
 said second protrusions being smaller than said first protrusions, so that said flow channels are constricted or interrupted in a region of said second protrusions; and 
 said second protrusions disposed in a region of a connecting line between said flow inlet and said flow outlet. 
 
 
     
     
       13. The electrochemical cell according to  claim 12 , wherein the electrochemical cell is a fuel cell.